Apparatus and method for controlling refrigerant temperature in a heat pump or refrigeration apparatus

ABSTRACT

An apparatus includes: a compressor including a pair of ports in fluid communication with first and second heat exchangers and a reduced temperature refrigerant inlet for receiving reduced temperature refrigerant; and an expansion device coupled between the first and second heat exchangers for reducing a pressure of refrigerant flowing from one of the first and second heat exchangers to the other of the first and second heat exchangers; wherein the compressor, the first heat exchanger, the expansion device and the second heat exchanger are arranged in a loop to operate as a refrigeration or heat pump apparatus.

FIELD OF TECHNOLOGY

The present disclosure relates to compressors for heat pump or refrigeration apparatus.

BACKGROUND

A typical refrigeration cycle is a closed loop system which uses a refrigerant having a low boiling point to produce a relative coldness. A compressor compresses the refrigerant in order to increase its pressure. As the pressure increases, the refrigerant gas temperature also rises and subsequently the gas then flows through a heat exchanger to transfer heat to the adjacent medium in the heat exchanger. As the heat dissipates, the refrigerant cools and condenses to a liquid. The liquid then flows through an expansion valve which causes the refrigerant to expand and change phases into a gas. The cold gas then circulates into a second heat exchanger and absorbs heat and then passes into the compressor where the cycle repeats.

Lubricant is provided in the compressor 12 to lubricate the compressor crankcase and other compressor components. Proper lubrication helps to avoid compressor failures, which can be costly both in terms of production down time and part replacement. The lubricant is intended to remain primarily in the compressor crankcase, however, the lubricant often migrates to other parts of a refrigeration apparatus.

In general, the temperature output of a refrigeration apparatus is limited by the effective temperature range of the lubricant and the compression process of the compressor. When operating above the effective temperature range, lubricants may break down over time in response to the high temperatures in the compressor. When the lubricant breaks down, the degraded lubricant may flow throughout the compressor and may cause compressor failure.

SUMMARY

In an aspect there is provided, an apparatus including: a compressor comprising a pair of ports in fluid communication with first and second heat exchangers and a reduced temperature refrigerant inlet for receiving reduced temperature refrigerant; and an expansion device coupled between the first and second heat exchangers for reducing a pressure of refrigerant flowing from one of the first and second heat exchangers to the other of the first and second heat exchangers; wherein the compressor, the first heat exchanger, the expansion device and the second heat exchanger are arranged in a loop to operate as a refrigeration or heat pump apparatus.

In another aspect there is provided a method including: compressing a refrigerant during a compression step of a refrigeration cycle; and injecting a reduced temperature refrigerant into a compressor part-way through the compression step.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present disclosure will now be described, by way of example only, with reference to the attached figures, wherein:

FIG. 1 is a cycle diagram of an apparatus according to an embodiment; and

FIG. 2 is a schematic top sectional view of a scroll compressor.

DETAILED DESCRIPTION

The following describes an apparatus and method of compressing a refrigerant during a compression step of a refrigeration cycle; and injecting a reduced temperature refrigerant into a compressor part-way through the compression step.

For simplicity and clarity of illustration, reference numerals may be repeated among the figures to indicate corresponding or analogous elements. Numerous details are set forth to provide an understanding of the embodiments described herein. The embodiments may be practiced without these details. In other instances, well-known methods, procedures, and components have not been described in detail to avoid obscuring the embodiments described. The description is not to be considered as limited to the scope of the embodiments described herein.

Referring to FIG. 1, an apparatus 10 is schematically shown by way of a cycle diagram. The apparatus 10 is generally a refrigeration apparatus, which may also be referred to as a heat pump. In general, the components of the apparatus 10 are arranged in a loop and refrigerant flows through the apparatus 10 in a first direction to generate heat at a first side of the apparatus 10. The flow may be reversed to switch the side of the apparatus 10 at which heat is generated.

The apparatus 10 includes a compressor 12, first heat exchanger 14 and second heat exchanger 16. A four-way reversing valve 18 is located between the compressor 12 and the heat exchangers 14, 16 to reverse the direction of fluid flow. First heat exchanger 14 and second heat exchanger 16 are both operable as an evaporator and a condenser depending on the direction of fluid flow through the apparatus 10. A first heat exchange conduit 28 communicates with the first heat exchanger 14 to transfer heat to the first heat exchanger 14 when the first heat exchanger 14 is operating as an evaporator and remove heat from the first heat exchanger 14 when the first heat exchanger 14 is operating as a condenser. Similarly, a second heat exchange conduit 30 communicates with the second heat exchanger 16 to transfer heat to the second heat exchanger 16 when the second heat exchanger 16 is operating as an evaporator and remove heat from the second heat exchanger 16 when the second heat exchanger 16 is operating as a condenser. The apparatus 10 further includes drive mechanisms (not shown) for pumping fluid through the first and second heat exchange conduits 28, 30.

A receiver 20 is located between the heat exchangers 14, 16. Refrigerant flowing from the first heat exchanger 14 enters the receiver 20 before flowing into the second heat exchanger 16. Similarly, when flow is reversed, fluid flowing from the second heat exchanger 16 enters the receiver 20 before flowing into the first heat exchanger 18. The receiver 20 is a reservoir for storing high pressure liquid. A volume of the receiver 20 is sized to compensate for expansion and contraction of the refrigerant in the constant volume apparatus 10.

A first valve 22 is located between the first heat exchanger 14 and the receiver 20 and a second 24 valve is located between the second heat exchanger 16 and the receiver 20. Both valves 22, 24 are capable of operating as expansion valves or as check valves, which are also referred to as one-way valves. The mode of operation of the valves 22, 24 depends on the direction of fluid flow through the apparatus 10. The valve 22, 24 that is located adjacent to an inlet of the heat exchanger operating as an evaporator operates as an expansion valve to reduce a pressure of the fluid entering the heat exchanger 14, while the valve 22, 24 that is located adjacent to an exit of the condenser operates as a check valve.

An accumulator 26 is located between the four-way reversing valve 18 and the compressor 12. The accumulator 26 is an optional component of the apparatus 10 and is generally provided to store excess liquid refrigerant and lubricant that may not have boiled off during evaporation.

Conduits, such as pipes, for example, are disposed between components of the apparatus 10 for conveying refrigerant therethrough. Conduit 32 is coupled between the compressor 12 and the four-way reversing valve 18. Conduit 34 is coupled between the four-way reversing valve 18 and the first heat exchanger 14. Conduits 36 and 38 are coupled between the first heat exchanger 14 and the valve 22 and the valve 22 and the receiver 20, respectively. Conduits 40 and 42 are coupled between the receiver 20 and the valve 24 and the valve 24 and the second heat exchanger 16, respectively. Conduit 44 is coupled between the second heat exchanger 16 and the four-way reversing valve 18. Conduit 46 is coupled between the four-way reversing valve 18 and the accumulator 26 and conduit 48 is coupled between the accumulator 26 and the compressor 12.

Conduits 32 and 48 are coupled to ports 50 and 52, respectively, of the compressor 12. The port 50 is an outlet port and the port 52 in an inlet port. The compressor 12 may have more than one inlet port 52.

A scroll compressor, which is shown schematically in FIG. 2, generally includes two inlet ports for receiving refrigerant from the evaporator. In a scroll compressor, refrigerant is compressed between two scroll plates that are nested together. One plate may be stationary while the other plate moves in an orbital path. Refrigerant is received through inlet ports at the perimeter of the scroll and as the plate orbits, an enclosed volume containing the refrigerant is transferred toward a decreased volume region at the center of the scroll. As the volume decreases, the refrigerant is compressed and discharged through an outlet port.

The compressor 12 further includes an injection inlet 54 for receiving a reduced temperature refrigerant from the receiver 20. Conduit 56 is coupled between the receiver 20 and an expansion valve 58 and conduit 60 is coupled between the expansion valve 58 and inlet 54 of the compressor 12 to facilitate delivery of the refrigerant to the compressor 12. The expansion valve 58 reduces a pressure of the refrigerant prior to the refrigerant entering the compressor 12. In a scroll compressor, the injection inlet 54 is located in interior or middle scrolls of the flanks of the scroll compressor.

The injection inlet 54 facilitates injection of refrigerant into the compressor 12 through the inlet 54 part-way through the compression step of the refrigeration cycle. In general, compressor outlet temperature is maintained below 300° F. in order to avoid damage due to lubricant breakdown. One or more of compressor outlet temperature, compressor motor temperature and compressor flank temperature are measured in order to determine when and how much of the reduced temperature refrigerant may be injected into the injection inlet 54. Methods for measuring compressor temperatures are well known in the art and therefore will not be described further.

The injection of reduced temperature refrigerant reduces the temperature of the refrigerant proceeding through the compression step and exiting the compressor 12. The reduced temperature refrigerant is less likely to cause the lubricant in the compressor to break down, which may result in an increased operating life of the compressor 12.

The refrigerant used in the apparatus 10 is Trifluoroiodomethane (CF3I), which may also be referred to as Iodotrifluoromethane, Monoiodotrifluoromethane, Trifluoromethyl iodide, Perfluoromethyl iodide or Freon 13T1. The chemical composition of the Trifluoroiodomethane includes one carbon atom combined with 3 flourine atoms and one Iodine atom. Sesquiterpene, which is a stabilizer may be added to the refrigerant

Alternatively, the refrigerant may be one of other blends fluorinated carbon compounds to facilitate the higher efficiency and work well with mid-compression refrigeration injection. The refrigerants generally have a low GWP (global warming potential) and are ozone friendly.

Operation of the apparatus 10 will now be described with reference to FIG. 1. In this example, heat exchanger 14 is operating as a condenser and heat exchanger 16 is operating as an evaporator.

Low pressure refrigerant enters the compressor 12 through port 52 and is compressed. Part-way through compression, reduced temperature refrigerant, which has a lower temperature than the refrigerant that is in the compressor 12, is injected through inlet 54. The reduced temperature refrigerant flows from the receiver 20, through the expansion valve 58, to enter the compressor 12 with a pressure that is lower than the pressure of the refrigerant in the receiver 20. The refrigerant entering the compressor 12 through the inlet 54 has an absolute pressure that is approximately mid-way between the absolute pressure at the inlet port 52 and the absolute pressure at the outlet port 50. The reduced temperature refrigerant mixes with the refrigerant in the compressor 12 and exits the compressor 12 through conduit 32 as a high pressure, high temperature gas. The refrigerant exiting the compressor 12 is at a high temperature, however, the temperature is less than the temperature would have been without the addition of the reduced temperature refrigerant, which facilitates protection of the lubricant and the moving mechanical parts of the compressor and other components of the apparatus 10.

The gas exiting the compressor 12 flows through the four-way reversing valve 18, through conduit 34 and enters the first heat exchanger 14. As the refrigerant flows through the first heat exchanger 14, the refrigerant is in indirect contact with fluid flowing through the first heat exchange conduit 28 to remove heat from the refrigerant. The condensed refrigerant exits the heat exchanger 14, flows through conduit 36 and travels past valve 22, which functions as a check valve. The condensed refrigerant then flows through conduit 38 and into the receiver 20.

The condensed refrigerant exits the receiver 20, flows through conduit 40 and travels past the valve 24, which functions as an expansion valve where the pressure of the refrigerant is reduced to facilitate expansion and lowering of the refrigerant temperature. The refrigerant then flows through conduit 42 and into the second heat exchanger 16. As the refrigerant flows through the second heat exchanger 16, the refrigerant is in indirect contact with fluid flowing through the second heat exchange conduit 30 and heat is absorbed by the refrigerant. As heat is absorbed, the refrigerant vaporizes and exits the second heat exchanger 16 through conduit 44 and flows into the four-way reversing valve 18. From the four-way reversing valve 18, the refrigerant flows through conduit 46 to enter the accumulator 26. The refrigerant then exits the accumulator 26 through conduit 48 and flows into the compressor 12 to begin the cycle again.

In general, the refrigerant temperature is maintained below a breakdown temperature of the lubricant. In one example, the refrigerant temperature is maintained 25 to 50 degrees Fahrenheit below the lubricant breakdown temperature. When Polyolester (POE), which is a common lubricant used with Hydro fluorocarbon (HFC) refrigerants, is used, the breakdown temperature is approximately 300 degrees Fahrenheit. Therefore, in this example, the temperature at the outlet port 50 of the compressor 12 may be between 250 and 275 degrees Fahrenheit.

In one embodiment, the four-way reversing valve 18 is eliminated from the embodiment of FIG. 1 and the apparatus 10 is operable in a single direction.

In another embodiment, a motor of the compressor 12 includes a frequency drive for controlling the compressor motor speed. There is a large difference between refrigeration densities at opposite ends of the operating conditions as determined by the refrigerant gas specific volumes and resultant density. For example, a compressor may need to move significantly more pounds of refrigerant gas for a particular pressure increase, which may consequently overload the connected refrigerant compressor motor. By slowing down the motor using a frequency drive, power input may be reduced. Control over the motor speed may improve the service life of the compressor 12.

In another embodiment, the reduced temperature refrigerant may be injected into the compressor 12 in response to a temperature at the outlet port 50 of the compressor 12 being within a predetermined temperature range. In one example, the reduced temperature refrigerant is injected into the compressor when the temperature at the outlet port 50 is between 250 and 275 degrees Fahrenheit.

The apparatus 10 described herein may include any type of compressor that is capable of compound and/or inter-stage compression. A scroll compressor is provided as an example and is not intended to be limiting.

By reducing the temperature of the refrigerant exiting the compressor 12, the operating life of the lubricant and therefore the operating life of the compressor 12 and other components of the heat pump/refrigeration apparatus may be extended.

In addition, by reducing the temperature of the refrigerant exiting the compressor 12, the efficiency of the refrigeration apparatus 10 may be increased. By achieving cooling/heating results more efficiently, the operating time of the refrigeration apparatus 10 may be reduced resulting in less energy consumed.

The present disclosure may be embodied in other specific forms without departing from its spirit or essential characteristics. The described embodiments are to be considered in all respects only as illustrative and not restrictive. The scope of the present disclosure is, therefore, indicated by the appended claims rather than by the foregoing description. All changes that come within the meaning and range of equivalency of the claims are to be embraced within their scope. 

What is claimed is:
 1. An apparatus comprising: a compressor comprising a pair of ports in fluid communication with first and second heat exchangers and a reduced temperature refrigerant inlet for receiving reduced temperature refrigerant; an expansion device coupled between the first and second heat exchangers for reducing a pressure of refrigerant flowing from one of the first and second heat exchangers to the other of the first and second heat exchangers; wherein the compressor, the first heat exchanger, the expansion device and the second heat exchanger are arranged in a loop to operate as a refrigeration or heat pump apparatus.
 2. An apparatus as claimed in claim 1, comprising an expansion device in fluid communication with the reduced temperature refrigerant port for reducing a pressure of the reduced temperature refrigerant entering the compressor.
 3. An apparatus as claimed in claim 1, comprising a receiver coupled between the first heat exchanger and the expansion device when fluid flow is from the first heat exchanger and the second heat exchanger.
 4. An apparatus as claimed in claim 1, comprising a receiver coupled between the second heat exchanger and the expansion device when fluid flow is from the second heat exchanger and the first heat exchanger
 5. An apparatus as claimed in claim 1, wherein two expansion devices are coupled between the first and second heat exchangers and a receiver is coupled between the pair of expansion devices, one of the two expansion devices being operable as a check valve.
 6. An apparatus as claimed in claim 5, wherein the reduced temperature refrigerant port is in fluid communication with the receiver.
 7. An apparatus as claimed in claim 1, wherein a volume of refrigerant flowing through the apparatus is generally constant.
 8. An apparatus as claimed in claim 1, wherein the reduced temperature refrigerant is Trifluoroiodomethane.
 9. An apparatus as claimed in claim 8, wherein sesquiterpene is added to the refrigerant.
 10. An apparatus as claimed in claim 1, wherein the compressor is a scroll compressor and the reduced temperature refrigerant inlet is located in a flank of the scroll compressor.
 11. An apparatus as claimed in claim 1, wherein the compressor is driven by a variable speed motor.
 12. A method comprising: compressing a refrigerant during a compression step of a refrigeration cycle; and injecting a reduced temperature refrigerant into a compressor part-way through the compression step.
 13. A method as claimed in claim 12, wherein the reduced temperature refrigerant is received from a receiver located between the condenser and evaporator.
 14. A method as claimed in claim 12, wherein the reduced temperature refrigerant is Trifluoroiodomethane.
 15. A method as claimed in claim 12, comprising measuring a temperature of the refrigerant at an outlet of the compressor and in response to the temperature being within a predetermined temperature range, injecting the reduced temperature refrigerant into a compressor part-way through the compression step. 